Flexible continuous sheet materials, whether they be polymer films, foamed polymer sheets, fabrics, wovens, non-wovens, paper, and the like, as well as multilayered structures of one or more of the foregoing, altogether “webs”, are typically manufactured as wide continuous sheets having widths of one meter or less to several meters or more. While certain processes allow for direct consumption of the so formed web sheets, most often the web sheets are wound into large, master rolls of dozens to hundreds of meters in length, one layer directly overlaying the previously wound layer. However, the vast majority of end-use applications for these web materials call for widths that are substantially less than the widths of the master rolls. Accordingly, it is common and a longstanding practice to slit the web materials into a plurality of strips of defined width(s) corresponding to the width(s) needed for a given end-use application.
In addition, certain applications also require lengths of the web materials that are less than those of the master rolls. One process of reducing both the width and the length of the wound web material is to unwind the master roll and rewind the web material on a sturdy, yet cuttable, core element until the desired length of the web material is wound on the core element. This smaller roll is then subject to a cutting process whereby the roll is cut through, i.e., through the web material and the core element, at the desired width(s). Most often, though, particularly where clean edges and/or high quality production as well as consistent widths are needed or desired, the web material is unwound from the master roll, slit into a plurality of strips of the desired width(s), and rewound onto a core element or, more commonly, a plurality of core elements, one for each strip of web material. Depending upon the width of the strip materials, the winding may be a roll winding where one layer is laid directly over the previously wound layer with the diameter of the roll growing with each successive winding. However, roll winding has its limits. Specifically, roll winding is appropriate for strips of widths of 15 cm or more, preferably 30 cm or more. While roll winding can also be used with strips of 10 cm or more or even 5 cm or more, the stability of the so-formed roll of strip web material is poor, especially as the diameter of the roll increases. Consequently, it is necessary to employ reels having side walls or elements as the core element. Strips of web materials having smaller widths, generally those of 15 cm or less, though possibly up to 25 cm, are typically wound on an elongated core element in a traverse winding process where successive windings are laid next to each other along the length of the core element, with or without overlap, until the end of the core element is reached at which point the winding moves in the opposite direction laying a layer of side-by-side strips, again with or without overlap, atop the previously laid layer until the starting point is reached and the process continues until the desired length of web material is attained or the end of the master roll is reached. Notwithstanding the latter comment, it is also known to splice the tail end of one master roll to the lead end of another master roll so that the slitting and rewinding process is continuous and each winding continues until the desired length of strip material is wound. This process is known as a traverse winding and is especially desirable as it allows for the formation of spools of strips of the web material that are much longer than the master rolls and much, much longer than can be attained with roll winding. With traverse wound spools, the end-user can run their manufacturing process much, much longer before needing to replace or switch out an expired spool for a new spool of the strip material. Nevertheless, despite the attributes and benefits of traverse winding, traverse winding adds another layer of complexity and sophistication to the winding apparatus not seen with roll winders.
Generally speaking, there are two methods by which traverse winding of strip materials is achieved, a center winding method and a surface winding method. In the former, a core element is slid on an axel driven by a motor which provides the rotational movement to the core element. These core winder motors are heavy duty and expensive as they require precise control with high torque capability due to the fact that these motors must adjust the speed and torque at which the core is driven to account for the growing weight and diameter of the spool. In this respect, it is to be appreciated that it is not uncommon for traverse wound spools of web materials to attain lengths of up to 30,000 to 50,000 meters, diameters of up to 122 centimeters (48 inches) and spool lengths of 92 centimeters (36 inches) and weights in excess of 50 kgs. Speed and tension control is especially important to achieve proper spooling without wrinkles, folds and misaligned laydowns on the spool as well as ensure that the web does not jump or fall from any of the roller and directional elements in its journey from the slitter to the laydown device. In this respect, it is important to maintain both speed and tension throughout the slitting process irrespective of the dwindling diameter of the master roll and the growing diameter of the spool. Furthermore, even with the best of core winder motors, the core winding process inherently introduces “cinching” in the rolls and an unevenness in the tightness of the strip web material between the inner layers and the outer layers as a result of the high torque, particularly as the spool gets heavier and heavier and the slippage of the wound materials. Additionally, core winding motors are not responsive or sensitive enough to accommodate light tension and make minor adjustments especially as the spools begin to get heavier and heavier. In any event, once the spool is complete, the spool is slid back off the axel and replaced with a new core element. Given the size and weight of the spool, it is oftentimes necessary to employ a lift device, such as a forklift or motorized roll lift, to remove the spool. This process can be slow and tedious resulting in long down times between winding sequences. Additionally, because each winding station must allow for the ingress and egress of a forklift, the overall process requires substantial workspace.
Surface winding, on the other hand, typically employs an axel with the core element slid thereon and secured thereto, wherein the axel extends beyond each end of the core element, with each extended end of the axel adapted to sit in a support cradle in which the axel is freely rotatable about its axis. A power driven roller is biased against the core element with sufficient pressure such that its rotation transfers the opposite rotation to the axel and core element assembly and, as the winding proceeds, the surface of the wound web material. A lay down head for depositing the slit web material is positioned on the opposite side of the axel from the power driven roller and, typically, is in a touch relationship with the core element and the winding. Both the power driven roller and the lay down head are retractable so that they move away from the spool as it grows in diameter while maintaining contact. Unlike the center winder, the motor driving the roller is simpler as it merely needs to maintain its speed of rotation in order for the surface speed of the spool and the draw of the web material to the spool to be held constant: this is so regardless of the diameter of the spool. When the spools are full, the spools are lifted out of the cradle by an appropriate crane-like apparatus. Most conveniently, an overhead rigging system is employed having a plurality of cross-beams each of which as a plurality of pairs of hook elements spaced and aligned so that when the rigging is overhead the spools, the cross-beams are lowered whereby the hooks engage with the ends of the axel and, when the cross-beam is raised the spools are lifted from the cradles. A second set of cross beams having hooks as well may be present, each spaced from a corresponding first set of cross beams except that these hooks carry a clean axel and core assembly. The rigging is moved in a lateral direction so as to center the second set of hooks over the empty cradles. The second set of cross beams is then lowered to set the new axels in place so that winding can be resumed. The rigging then moves beyond the winders so that the spools of web material can be laid on the floor or on appropriate wagons for subsequent storage. Clean axels are added to the hooks of the second set of cross beams awaiting the next switch-out of the spools. Although convenient and allowing for the replacement of multiple winding elements at one time, the rigging superstructure is expensive and bulky and, more importantly, the process area required for this set up is essentially double since the rigging must clear the existing winding units to unload.
Another factor affecting the simplicity, cost and workspace requirement of the winding process is the nature of the traverse winding itself. Specifically, there are two methods for achieving transverse winding: a stationary winder or a stationary laydown. The former requires the least workspace; however, because the laydown head is continuously traversing back and forth across the face of the core element and growing spool, the length of the path of the web material is constantly changing. Consequently, more sophistication is needed in the laydown assembly to accommodate the changing path as well as in the process control system and logic to ensure that the laydown speed and tension remains substantially constant. Any deviation in movement of the strip of web material resulting in an increase in the tension thereof can cause a stretching and, at the extreme, breaking of the strip of web material. Stretching may be permanent and/or may cause the web material to fold upon itself in the lengthwise direction. Depending upon the nature of the web material itself, the fold may be permanent and lead to an out-of-specification product. Conversely, a deviation may result in too little tension or a slack in the web which may result in the strip of web material jumping or sliding off a roller element in the winding system. Alternatively, or in addition, the slack may result in a bunching up or fold across the width of the strip which becomes wound into the spool: again resulting in a defect finished product. Furthermore, this necessitates the shutting down of the slitting and winding operation so that the web materials may be properly placed back on the roller and guide system.
The second method is that where the laydown head and apparatus is stationary and the winding apparatus comprising the drive motors effecting the winding and the winders themselves are set upon a moving carriage or sled assembly whereby the carriage or sled oscillates such that the core element moves back and forth along its length while the lay down head, which is stationary, lays the web material on the core element and growing spool. This apparatus, while preferred, requires a greater capital commitment since the carriage or sled must also carry the drive means for the winding process as well as a much large footprint since the sled must traverse a distance at least as great as the largest core elements to be used.
Despite all of the advances made in the slitting and winding of web materials there is still a need for new and improved systems and apparatus for use in the slitting and winding of web materials, particularly given the competitive nature of the industry and the realization that even minor changes in the cost and efficiency lead to huge savings in light of the volume of materials processed. In particular, there is a need for simpler and less costly apparatus, for apparatus and systems that have less concern or even eliminate downtime and defects arising from poor tension and speed control, for apparatus and systems that have less special requirements, as well as, finally, systems that achieve the foregoing while increasing capacity, efficiency and throughput.
Finally, there is a need for systems that achieve all or substantially all of the foregoing needs while also having far less spatial requirements. Indeed, land costs, construction costs, facilities maintenance, etc., all add to the increasing burden of manufacture and processing. Being able to reduce those needs leads to additional overall cost savings